B Vitamins And Folate May Not Prevent Cancer

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Main Category: Nutrition / Diet
Also Included In: Cancer / Oncology;  Breast Cancer
Article Date: 05 Nov 2008 - 0:00 PDT

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According to a report published in the November 5 issue of JAMA, women with a high risk of cardiovascular disease who took a daily supplement of folic acid and vitamins B6 and B12 did not seem to reduce their likelihood of developing cancer - including breast cancer.

Although the cancer-preventing powers of folate and the water-soluble, essential vitamins B6 and B12 seemed to have permeated the public consciousness, there is no conclusive evidence defending their roles. Shumin M. Zhang, M.D., Sc.D. (Brigham and Women's Hospital and Harvard Medical School, Boston) and colleagues write that, "Background fortification of the food supply with folic acid (a synthetic form of folate), a policy that began in the United States in 1998 to reduce risk of neural tube defects, has improved folate status in the general population. Approximately one-third of U.S. adults currently take multivitamin supplements containing folic acid, vitamin B6, and vitamin B12." However, randomized trials testing how folic acid alone or with B vitamins impacts cancer risk are limited and inconsistent. One trial has even suggested that the compounds may be harmful to the body.

To evaluate how the combined effects of folic acid, vitamin B6, and vitamin B12 treatment impact cancer risk, Zhang and colleagues conducted a study with a sample of women who were at high risk for cardiovascular disease. The sample consisted of 5,442 U.S. female health professionals age 42 years and over who participated in The Women's Antioxidant and Folic Acid Cardiovascular Study. The women had pre-existing cardiovascular disease or three or more coronary risk factors. Researchers randomly assigned the women so that 2,721 received a daily combination of folic acid (2.5 mg.), vitamin B6 (50 mg.), and vitamin B12 (1 mg.) and 2,721 received a matching placebo. The study lasted from April 1998 to July 2005 - 7.3 years.

"A total of 379 women developed invasive cancer (187 in the active treatment group and 192 in the placebo group)," found the authors. "Compared with placebo, women receiving the active treatment had similar risk of developing total invasive cancer, breast cancer, or any cancer death." The researchers also verify that at baseline, the groups did not differ in their use of multivitamin supplements, intakes of total folate, vitamin B6, and vitamin B12, or cancer history.

One factor, age, was found to significantly modify the way in which combined B vitamin treatment affected the risk of total invasive cancer and breast cancer. Women age 65 years or older at study entry had a significantly reduced risk of total invasive cancer and breast cancer, while younger women (40-54 or 55-64 years old) did not have this reduction in risk. Zhang and colleagues add that, "If the finding is real and substantiated, the results may have public health significance because the incidence rates of cancer are high in elderly persons. The finding is biologically plausible because elderly individuals have increased requirements for these B vitamins."

"Treatment with combined folic acid, vitamin B6, and vitamin B12 provided neither beneficial nor harmful effects on overall risk of total cancer, breast cancer, or deaths from cancer among women at high risk for CVD," conclude the researchers.

Effect of Combined Folic Acid, Vitamin B6, and Vitamin B12 on Cancer Risk in Women: A Randomized Trial
Shumin M. Zhang; Nancy R. Cook; Christine M. Albert; J. Michael Gaziano; Julie E. Buring; JoAnn E. Manson
JAMA (2008); 300[17]: pp. 2012-2021.
Click Here to View Abstract

Written by: Peter M Crosta
Copyright: Medical News Today
Not to be reproduced without permission of Medical News Today

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